maria grazia pia infn genova [email protected] salamanca, 15-19 july 2002
TRANSCRIPT
Maria Grazia Pia
Maria Grazia PiaINFN Genova
Salamanca, 15-19 July 2002
http://cern.ch/geant4/geant4.htmlhttp://www.ge.infn.it/geant4/events/salamanca.html
Basics of a user Basics of a user applicationapplication
Maria Grazia Pia
Maria Grazia Pia
The main program
Geant4 does not provide the main()
In his/her main(), the user must– construct G4RunManager (or his/her own derived class)– notify the mandatory user classes to G4RunManager
G4VUserDetectorConstruction
G4VUserPhysicsList
G4VUserPrimaryGeneratorAction
The user can define – VisManager, (G)UI session, optional user action classes, one’s
own persistency manager, an AnalysisManager… in his/her main()
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User classesInitialization classesInitialization classesInvoked at the initialization
G4VUserDetectorConstruction
G4VUserPhysicsList
Action classesAction classesInvoked during the execution loop
G4VUserPrimaryGeneratorAction
G4UserRunAction
G4UserEventAction
G4UserStackingAction
G4UserTrackingAction
G4UserSteppingAction
Mandatory classes:
G4VUserDetectorConstruction describe the experimental set-up
G4VUserPhysicsList select the physics you want to activate
G4VUserPrimaryGeneratorAction generate primary events
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Describe the experimental set-up
Derive your own concrete class from the G4VUserDetectorConstruction abstract base class
Implement the Construct() method (modularise it according to each detector component or sub-detector)
– construct all necessary materialsmaterials– define shapes/solidsshapes/solids required to describe the geometry– construct and place volumes volumes of your detector geometry– define sensitive detectorssensitive detectors and identify detector volumes to associate
them to– associate magnetic fieldmagnetic field to detector regions– define visualisation attributesvisualisation attributes for the detector elements
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Select physics processes
Geant4 does not have any default particles or processes– even for the particle transportation, one has to define it explicitly
Derive your own concrete class from the G4VUserPhysicsList abstract base class
– define all necessary particlesparticles– define all necessary processes processes and assign them to proper particles– define production thresholdsproduction thresholds (in terms of range)
Read the Physics Reference Manual first!Read the Physics Reference Manual first!
The Advanced Examples offer a guidance for various typical experimental The Advanced Examples offer a guidance for various typical experimental domainsdomains
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Generate primary events
Derive your concrete class from the G4VUserPrimaryGeneratorAction abstract base class
Pass a G4Event object to one or more primary generator concrete class objects, which generate primary vertices and primary particles
The user can implement or interface his/her own generator– specific to a physics domain or to an experiment
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Optional user action classesG4UserRunActionG4UserRunAction
BeginOfRunActionBeginOfRunAction(const G4Run*)– example: book histograms
EndOfRunActionEndOfRunAction(const G4Run*)– example: store histograms
G4UserEventActionBeginOfEventActionBeginOfEventAction(const G4Event*)
– example: event selection
EndOfEventActionEndOfEventAction(const G4Event*)– example: analyse the event
G4UserTrackingActionPreUserTrackingActionPreUserTrackingAction(const G4Track*)
– example: decide whether a trajectory should be stored or not
PostUserTrackingActionPostUserTrackingAction(const G4Track*)
G4UserSteppingActionG4UserSteppingActionUserSteppingActionUserSteppingAction(const G4Step*)
– example: kill, suspend, postpone the track
G4UserStackingActionG4UserStackingActionPrepareNewEventPrepareNewEvent()
– reset priority control
ClassifyNewTrackClassifyNewTrack(const G4Track*)– Invoked every time a new track is pushed – Classify a new track (priority control) Urgent, Waiting, PostponeToNextEvent,
Kill
NewStage()NewStage()– invoked when the Urgent stack becomes
empty– change the classification criteria – event filtering (event abortion)
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Select (G)UI and visualisation
In your main(), taking into account your computer environment, construct a G4UIsession concrete class provided by Geant4 and invoke its sessionStart() method
Geant4 provides:– G4UIterminalG4UIterminal csh or tcsh like character terminal– G4GAG G4GAG tcl/tk or Java PVM based GUI– G4WoG4Wo Opacs– G4UIBatchG4UIBatch batch job with macro file– etc…
Derive your own concrete class from G4VVisManager, according to your computer environment
Geant4 provides interfaces to various graphics drivers:
– DAWNDAWN Fukui renderer – WIREDWIRED– RayTracerRayTracer ray tracing by Geant4 tracking– OPACSOPACS– OpenGLOpenGL– OpenInventorOpenInventor– VRMLVRML
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Initialisationmain Run manager user detector
const ructionuser physics
list
1: initialize2 : const ruct
3: material const ruct ion
4: geometry construct ion5: world volume
6 : const ruct
7 : physics process const ruction
8: set cuts
Describe a geometrical set-up: a Si-W tracker, a CsI calorimeter and an anti-coincidence system made out of plastic scintillators.
Activate electromagnetic/hadronic
processes appropriate to the energy range of the experiment
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Beam On
main Run Manager Geometry manager
Event generator
EventManager
1: Beam On2: close
3: generate one event
4: process one event
5: open
Generate primary events according to various distributions relevant to gamma astrophysics
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Event processing
Event manager
Stacking manager
Tracking manager
Stepping manager
User sensitive detector
1: pop
2: process one track3: Stepping
4: generate hits
5: secondaries
6: push
Record the coordinates of impact of tracks in the tracker layersRecord the energy deposited in each element of the calorimeter at every event